1. Field of the Invention
The present invention relates to a draft chamber and in particular, to a draft chamber in which a chemical liquid vessel is provided that is used to chemically clean and etch a silicone wafer or the like in a process for manufacturing a semiconductor.
2. Description of the Related Art
A semiconductor manufacturing process includes a step of chemically cleaning and etching a silicone wafer. For example, in the chemical cleaning step, the silicone wafer is immersed and treated for a period of time of 10 to 20 minutes in a vessel containing a chemical solution composed of hydrogen peroxide, ammonia, hydrochloric acid, sulfuric acid and the like heated up to high temperatures (80.degree. C. - 120.degree. C.). Also, in the etching step, the silicone wafer is immersed in a vessel containing a chemical solution composed of fluoric acid, nitric acid and the like for a period of time of several minutes.
Now, the above-mentioned processes for treatment of the silicone wafer are carried out within a draft chamber which is provided in a clean room, in order to prevent the wafer from being attached by dust or the like.
In a conventional draft chamber of this type, in order to prevent toxic gasses, which are generated from the chemical solution vessel, from leaking into the clean room, there is provided a duct for exhaustion so that the toxic gasses can be exhausted externally through the exhaust duct by means of driving of a fan.
According to the conventional draft chamber, however, due to the fact that the exhaustion is executed in such a manner that the toxic gasses are dispersed and mixed with the air in the draft chamber, the air existing within the clean room for air conditioning is also exhausted in a large amount together with the toxic gasses by a fan of a large capacity. As a result of this, a large amount of air is wasted and also, due to the fan driving, much power is required.